Boris Johnson has warned of a huge loss of life if lockdown measures are lifted too soon, as he urged Britons to “contain their impatience” during the fight against coronavirus.

In his first address to the nation since returning to work after being treated in intensive care, the prime minister said the UK is now beginning to “turn the tide” in the battle against COVID-19, but that Britain is also now at “the moment of maximum risk”.

Johnson, speaking outside 10 Downing Street on Monday morning, said that while Britain has “begun to wrestle coronavirus to the floor”, he was not prepared to risk a second peak by easing government guidance too early.

The prime minister said: ‘I’m sorry I’ve been away from my desk for much longer than would’ve liked, and I want to thank everyone who has stepped up, in particular Dominic Raab who has done a terrific job.

Prime Minister Boris Johnson makes a statement outside 10 Downing Street, London, as he resumes working after spending two weeks recovering from Covid-19.

Prime Minister Boris Johnson makes a statement outside 10 Downing Street, London, as he resumes working after spending two weeks recovering from Covid-19.

Prime Minister Boris Johnson speaking in Downing Street, London, as he resumes working from his office after spending two weeks recovering from Covid-19.

“But once again I wanted to thank you, the people of this country, for the sheer grit and guts you’ve shown and continue to show every day. I know this virus brings new sadness and mourning to households across the land, and it’s still true – this is the biggest single challenge this country has faced since the war.”

He later added: “If this virus were a physical assailant, an unexpected and invisible mugger, which I can tell you from personal experience it is, then this is the moment we have begun together to wrestle it to the floor, so this is the moment of opportunity when we can press home our advantage.

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“It’s also the moment of maximum risk because there will be many people looking at our current situation and success, and beginning to wonder, whether now is the time to go easy on social distancing measures.

“I know how hard and stressful it has been to give up, even temporarily, those ancient and basic freedoms – not seeing friends, not seeing loved ones, working from home, managing the kids, worrying, about your job and your firm.

MP's Social distancing as Foreign secretary Dominic Raab speaks during Prime Minister's Questions in the House of Commons, London.

“So let me say directly to British business, to entrepreneurs, to shopkeepers, to the hospitality sector, to everyone on whom our economy depends, I understand your impatience and share your anxiety, and without our private sector there will be no economy to speak of, no cash to pay for our public services, no way of funding our NHS.

“I can see the long-term consequences of lockdown as clear as anyone and I share your urgency, but we must also recognise the risk of a second spike, or losing control of the virus and letting the reproduction rate go over 1, because that would mean a new wave of death and disease but also economic disaster and we’d be forced to slam on the brakes on the country and the economy.”

In a direct plea to the nation, Johnson said: ‘I ask you to contain your impatience, because we are coming now to the end of the first phase of this conflict and inspire of all the suffering we have nearly succeeded.

‘We defied so many predictions, we did not run out of ventilators or ICU beds, we did not allow our NHS to collapse, and on the contrary we have so far collectively shielded our NHS so our incredible doctors, nurses and NHS staff have been able to shield all of us.

Johnson said: “I want to get this economy moving as fast as I can” but added: “I refuse to throw away all the effort and the sacrifice of the British people and to risk a second major outbreak and huge loss of life.”

The prime minister has resumed full-time duties at the head of the government, three weeks after he was admitted to hospital with the disease.

He will chair the regular morning meeting of the government’s COVID-19 “war cabinet” before heading into a series of meetings with senior ministers and officials.

Johnson – who spent a week in St Thomas’ Hospital in London, including three nights in intensive care – is said to be determined to ensure that there is no second peak.

The pressure to begin easing the restrictions came from a series of wealthy Tory backers who called over the weekend for the government to allow the economy to restart.

The prime minister has less than two weeks before the next major decision point comes up, with the next three-week review of the lockdown restrictions due on 7 May.

Foreign secretary Dominic Raab has said the government is doing its “homework” in preparation for when the rules could be eased.

It is thought that among the first moves could be a re-opening of schools, although Raab said that would be “inconceivable” without some further measures in place.